Rolling of metal

ABSTRACT

A method of rolling metal comprising the placing together of at least two metal plates in overlapping relation so that as they are rolled each plate indents the other and at least one of the plates becomes a rolled product having relatively thin and relatively thick parts spaced in the direction of rolling. The rolled product may form a turbine blade blank with an integral root portion.

United States Patent [191 Thompson ROLLING 0F METAL [75] Inventor: Raymond Thompson, Dore, England [73] Assignee: Osborn Steels Limited, Ecclesfield,

Sheffield, England [22] Filed: Aug. 10, 1973 {21] Appl. No.: 387,530

[30] Foreign Application Priority Data Aug. 21, 1972 Great Britain 38898/72 [52] US. Cl. 72/363, 29/156.8 B, 29/423, 29/480, 72/365 [51] Int. Cl B2111 31/00, B2lb l/38, B21k 3/04 [58] Field of Search. 29/DIG. 18, DIG. 20, DIG. 32, 29/DIG. 48, 156.8 B, 156.8 P, 423, 426, 480;

[56] References Cited UNITED STATES PATENTS 1,956,818 5/1934 Acre 72/366 2,471,486 5/1949 Gruetjen... 29/156.8 P 2,742,076 4/1956 Klein 29/423 X 1 ,lan.7,1975

2,804,681 9/1957 Brueckner 29/423 X 2,851,770 9/1958 Fromson 3,119,289 l/l964 Bach 3,561,099 2/1971 Mizuhara 3,588,980 6/1971 Cogan 3,628,226 12/1971 Nelson 29/480 X FOREIGN PATENTS OR APPLICATIONS 416,248 7/1925 Germany 72/365 727,985 4/1955 Great Britain 72/377 Primary Examiner-C. W. Lanharm Assistant Examiner-E. M. Combs Attorney, Agent, or FirmArman.d E. Lackenbach [57] ABSTRACT A method of rolling metal comprising the placing together of at least two metal plates in overlapping relation so that as they are rolled each plate indents the other and at least one of the plates becomes a rolled product having relatively thin and relatively thick parts spaced in the direction of rolling. The rolled product may form a turbine blade blank with an integral root portion.

4 Claims, 9 Drawing Figures PATENTED JAN 7 I 5 SHEET 2 UP 2 ROLLING or METAL The invention relates to the rolling of metal and has for its object to provide an improvement therein. In particular, the invention relates to a method of rolling metal which is particularly useful in the manufacture of turbine, fan and compressor blades for aircraft engines and propellers and also to steam turbine blades, and possibly also to other bladed articles such as paddles, (hereinafter generally referred to as turbine blades) that is to say to a method of producing such blade blanks.

If a rolled product is to have a varying cross-sectional shape it is customary to achieve this by the use of rolls which are contoured accordingly. However, this does not always result in the grain flow required and the production of the special non-cylindrical rolls is expensive. In addition, there is a limitation on the width of product which can be produced by this method, that is to say the length of the rolls. The only other methods of producing a rolled product of varying cross-sectional shape have been to effect a rolling operation in what may be termed an intermittent manner by the use of generally cylindrical rolls having axially extending grooves or flats, or to effect a rolling operation between a pair of cylindrical rolls the spacing of which has been controlled according to the product thickness required as rolling has proceeded, as in the production of taper rolled products. These known methods may have resulted in the grain flow required but in the first instance the production of the special rolls required has been very expensive and there are obvious limitations on the rolled products which can be produced and in the second instance the provision of apparatus for controlling the spacing of the rolls according to the product thickness required is very expensive and of course there is a limitation on the rate of increase in thickness along a rolled product imposed by the radius of each roll.

According to one aspect of the invention, there is provided a method of rolling metal, the method including the steps of placing at least two metal plates to gether in overlapping relation so that at least one of said plates extends beyond the other, entering said plates together into the gap between a pair of rolls and performing a rolling operation so that each plate indents the other over the area by which they overlap each other, and subsequently separating s'aid plates from each other. The plates will preferably be temporarily secured together initially by being tack welded together along their edges, and the plates may be placed together so that the plate which extends beyond the other does so by an amount substantially equal to the desired length of the thickest part of the resulting rolled product, in which case there need be little or no reduction in thickness of that part of the plate during the subsequent rolling operation. n the other hand, the plates may be placed together so that the plate which extends beyond the other does so by an amount less than the desired length of the thickest part of the resulting rolled product, in which case the reduction in thickness of that part of the plate during the subsequent rolling operation will be such as to bring about the required elongation. The ends of the metal plates may be straight and extend at right angles to the length of the plates. On the other hand one end of at least one. of said plates may be contoured so that a line of transition between thinnest and thickest parts of the resulting rolled product formed by the other plate will be similarly contoured. The metal plates which are initially placed together in overlapping relation may be of uniform thickness along their length so that the thinnest part of the resulting rolled product is of uniform thickness along its length. Alternatively, the metal plates which are ini tially placed together in overlapping relation may be oppositely tapered so that the thinnest part of the re sulting rolled product will be tapered accordingly. Each pair of plates may be of equal or substantially equal length so that each one overlaps the other by the same or substantially the same amount and so that there is thus produced two lengths of resulting rolled product having relatively thin parts of equal length and relatively thick parts of equal length, the transition be tween the relatively thin and relatively thick parts of each such length being relatively sudden. A plurality of metal plates may be temporarily secured together successively in overlapping relation to form a ribbon of plate stock before the rolling operation is carried'out. Alternatively, a plurality of metal plates may be secured together in overlapping sandwich fashion before the rolling operation is carried out.

According to another aspect of the invention, there is provided a length of rolled product having a relatively thin part and a relatively thicker part, the two parts being spaced apart in the direction in which roll ing has been effected and the transition between the relatively thin and relatively thick parts being relatively sudden, the product having been produced by the method described above.

According to a still further aspect of the invention, there is provided a method of producing a turbine blade, the method including the step of producing an elongate'blade blank element and integral root portion by placing at least two metal plates together in overlapping relation, rolling them as described above, and sub- 7 sequently separating said plates from each other so that at least one of said platesconstitutes an elongate blade blank element, formed by an indented area of the plate, and an integral root portion formed by a part of the plate which extended beyond the other plate during the rolling operation. The-method will include the further steps of shaping the blade blank element to the outline shape required and the forming of the shaped blade blank to the required aerofoil section. The method may also include the bringing together of a pair of shaped blade blanks before or after their forming to the required aerofoil section, and their welding together around their edges to form a blade blank of hollow form. The blade blank thus formed may be finally ground to the exact outline shape and form required.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings of which:

FIGS. 1 and 2 are diagrammatic views which illustrate steps in carrying out the method of rolling metal the subject of this invention,

FIG. 3 is a perspective view illustrating a resulting rolled product,

FIGS. 4 and 5 are diagrammatic views illustrating initial steps in modifications of the method,

FIG. 6 is a view similar to FIG. 3 and illustrating a resulting rolled product,

FIG. 7 is a diagrammatic view which illustrates a further possible modification, and

FIGS. 8 and 9 are perspective diagrammatic views which illustrate the use of the method for making turbine blades.

Referring now to FIG. 1, an initial step in carrying out the invention has involved the placing together of two metal plates 10 and 12 in overlapping relation so that each overlaps the other by a distance d; The plates have then been temporarily tack welded together as shown along their side edges and entered together into the gap between a pair of rolls, shown in chain-dotted lines, so that over a distance D, that is to say over an area by which the plates overlap each other, each plate indents the other during a rolling operation or successive rolling operations in the direction in which the plates overlap. In FIG. 2 it can be seen that ifthe reduction in thickness is such that over the distance by which they overlap each other the plates are each reduced to half their initial thickness, they each increase in length to substantially 2D whereas the portion of each plate which extends beyond the adjacent end of the other is not reduced in thickness and consequently retains its initial length.

When the plates have been subsequently separated from each other by breaking away the tack welding, each has been found to have the form shown in FIG. 3, that is to say have relatively thin and relatively thick parts spaced in the direction in which rolling has taken place, as indicated by the arrows, and in which the grain flow has been arranged by the rolling operation. The transition between the relatively thin and relatively thick parts is relatively sudden, that is to say far more sudden than could normally be achieved in the direction of rolling.

Various modifications may be made without departing from the scope of the invention. For example, the

ends of the metal plates shown in FIGS. 1 and 2 have been straight and extend at right angles to their length. Consequently, the line of transition between the relatively thin and relatively thick parts of each resulting rolled product has also been straight and has extended at right angles to the length of the product. However, it would notbe outside the scope of the invention to give one end of at least one of the plates a contoured form so that the line of transition between the relatively thinner and relatively thicker parts of the rolled product formed by the other plate would be similarly contoured, as shown by the chain-dotted line in FIG. 3 for example. Furthermore, in FIG. 4 there is illustrated the initial step of performing the invention in which a plurality of metal plates have been secured together successively in overlapping relation to form a ribbon of plate stock before a rolling operation is carried out. It will be understood that in this case, after the rolling operation has been carried out and the plates have been separated by breaking away the welds, each rolled product will comprise relatively thin end lengths joined together by a relatively thick intermediate length (and of course each can be cut in half if what is required is a length of rolled plate with a thicker end portion). On the other hand, in FIG. 5 there is illustrated the initial step of performing the invention in which five metal plates have been placed together in what can be termed overlapping sandwich fashion before a rolling operation is carried out. As shown in chain-dotted lines in FIG. 5 and in perspective view in FIG. 6, the rolling operation will reduce the thickness of each of the three intermediate plates equally from both sides so that the relatively thicker part of each rolled product will be concentrically arranged about the longitudinal centre line of the thinner part. Each one of the outermost plates will assume the form of the rolled product shown in FIG. 3, but of course it will be understood that the same degree of reduction cannot here be achieved if the metal plates are all initially of the same thickness as shown. However, it will be understood that'the metal plates may initially be of differing thicknesses to enable required rolled products of different thicknesses to be produced. It will also be understood that any number of metal plates may be placed together in the manner described to produce the kind of rolled product made possible by this invention. It is of course not necessary for only the overlapping areas of the plates to be reduced in thickness. The relatively thicker parts could also be reduced in thickness (and in fact it is advantageous that they should be in order that grain flow brought about in the direction of rolling along the relatively thinner parts will be maintained along the relatively thicker parts) but of course whatever the degree of reduction effected, the ratio between the thicker and thinner parts of the resulting rolled product will be maintained.

Referring now to FIG. 7, this diagrammatically illustrates a further modification of the invention in which a pair of oppositely tapered metal plates 14 and 16 have been placed together in overlapping relation prior to a rolling operation being carried out. Consequently, after rolling, the relatively thinner parts of the rolled product will be tapered accordingly, the amount of taper of the rolled product being dependent on the elongation, that is to say on the degree of reduction taking place during the rolling operation. It will be understood that in all these various ways of carrying out the invention a simple kind of rolling mill apparatus with cylindrical rolls can be employed. It will also be understood that there are no limitations imposed on the lengths of the relatively thin and relatively thick parts of the rolled product.

Referring now to FIGS. 8 and 9, these illustrate the use of the method for making turbine blades of hollow form for aircraft engines. In FIG. 8 there is illustrated a rolled plate such as illustrated in FIG. 3, that is to say having relatively thin and relatively thick parts spaced in the direction in which rolling has taken place, as indicated by the arrows, and the subsequent operation of shaping the blade blank element B to the outline shape of the finished blade required is shown by the chain.- dotted lines. There is thus produced an elongate blade blank element of relatively thin section formed by an indented area of the plate with an integral root portion formed by a part of the plate which extended beyond the other plate during the rolling operation; The'forming of the shaped blade blank to the required aerofoil section (that is to say to the shape of one face of the blade required) will then be effected and a pair of such shaped and formed blade blanks with integral root portions will subsequently be brought together back to back, as shown in FIG. 9, to be welded together around their edges and finally ground to the exact outline shape and form required.

Various other modifications may be made without departing from the scope of the invention. For example it will be understood that the method of rolling can be used for the manufacture of turbine blades of solid construction in which case a rolled plate as illustrated in FIG. 3 will be shaped and formed on both sides to the required aerofoil section. It will also be understood that the method may also be useful in the manufacture of other bladed articles, for example steam turbine blades and propellers and paddles of various kinds.

It will be understood that the method of rolling, whether or not the resulting rolled product is a turbine blade blank with integral root portion, may be such that only one of two metal plates which have been initially placed together extends beyond the other. In this case, after a rolling operation has been carried out and the plates separated, it will be found that only one of said plates will have a relatively thin part and a relatively 1. In a method of producing a turbine blade and inte gral root portion, the step of producing an elongate blade blank element and integral root blank portion by placing two metal plates together in overlapping relation so that at least one of said plates extends beyond the other, entering said plates together into the gap between a pair of rolls and performing a lengthwise rolling operation so that each plate indents the other over the area by which they overlap each other to form in at least one of said plates, a relatively thin elongate blade blank element integral with a relatively thick root blank portion, said blade element and root portion being separated by a sudden transition portion normal to both said blade element and root portion, so that in said one plate continuous grain flow is produced along the indented area which forms the part which constitutes said elongate blade blank element and longitudinally of the part which constitutes said relatively thicker integrally formed root blank portion despite the transition between the blade blank element and the integral root blank portion in the direction in which rolling has been effected being relatively sudden, and sub sequently separating said plates from each other.

2. In a method of producing a turbine blade according to claim 1, the further steps of shaping the blade blank element to the outline shape required. and of forming the shaped blade blank to the required aerofoil section.

3. In a method of producing a turbine blade according to claim 2, the further steps of bringing together a pair of the shaped and formed blade blank elements and of welding themtogether around their edges to form a blade of hollow formi 4; In a method of producing a turbine blade according to claim 3, the further step of finally grindingthe blade of hollow form to the exact outline shape and form required.

l= a: a: 

1. In a method of producing a turbine blade and integral root portion, the step of producing an elongate blade blank element and integral root blank portion by placing two metal plates together in overlapping relation so that at least one of said plates extends beyond the other, entering said plates together into the gap between a pair of rolls and performing a lengthwise rolling operation so that each plate indents the other over the area by which they overlap each other to form in at least one of said plates, a relatively thin elongate blade blank element integral with a relatively thick root blank portion, said blade element and root portion being separated by a sudden transition portion normal to both said blade element and root portion, so that in said one plate continuous grain flow is produced along the indented area which forms the part which constitutes said elongate blade blank element and longitudinally of the part which constitutes said relatively thicker integrally formed root blank portion despite the transition between the blade blank element and the integral root blank portion in the direction in which rolling has been effected being relatively sudden, and subsequently separating said plates from each other.
 2. In a method of producing a turbine blade according to claim 1, the further steps of shaping the blade blank element to the outline shape required and of forming the shaped blade blank to the required aerofoil section.
 3. In a method of producing a turbine blade according to claim 2, the further steps of bringing together a pair of the shaped and formed blade blank elements and of welding them together around their edges to form a blade of hollow form.
 4. In a method of producing a turbine blade according to claim 3, the further step of finally grinding the blade of hollow form to the exact outline shape and form required. 